300-420 Question #312: Real Exam Question with Answer & Explanation

Question

A company has many spoke sites with two data centers. The company wants to exchange the routing information between the data centers and the spoke sites using EIGRP. All locations belong to a single AS, and auto-summarization is disabled. Which two actions must the company choose? (Choose two.)

Options

• ASplit the network into two separate ASs.
• BExchange all routes between locations.
• CSummarize the routes between the hubs.
• DMake each spoke site router a stub router.
• ESummarize the routes from spokes to the hubs.

Explanation

To optimize EIGRP routing in a hub-and-spoke topology with a single AS and disabled auto-summarization, configure spoke routers as stub routers and summarize routes from the spokes at the hub.

Common mistakes.

• A. Splitting the network into two separate ASs would add unnecessary complexity and goes against the requirement of having all locations within a single EIGRP AS.
• B. Exchanging all routes without summarization would lead to excessively large routing tables, increased convergence times, and higher resource consumption, which is inefficient for a large hub-and-spoke network.
• C. Summarizing routes between the hubs is not the primary optimization point; the focus should be on summarizing the numerous granular routes originating from the spokes to reduce the overall routing table size.

Concept tested. EIGRP hub-and-spoke optimization

Reference. https://www.cisco.com/c/en/us/td/docs/ios-xml/ios/iproute_eigrp/configuration/15-mt/ire-15-mt-book/ire-stub-rt.html

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